[gtksourceview] c.lang: highlight _t and _T types as c:type

[Christian Hergert <chergert src gnome org>]

commit cf4f362a5e8fb4b5a49848e6057176feea61740c
Author: Rosetta H&S <markredmann icloud com>
Date:   Sun Jan 2 13:41:21 2022 -0600

    c.lang: highlight _t and _T types as c:type
    
    The following modifications provides automatic C/C++ syntax highlighting
    of user-defined types
    [ending with either "_t" or 
"_T"](https://stackoverflow.com/questions/231760/what-does-a-type-followed-by-t-underscore-t-represent),
    as is seen in editors/viewers such as Nano, Micro, Stack Overflow, or
    within GitHub itself.

 data/language-specs/c.lang | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/data/language-specs/c.lang b/data/language-specs/c.lang
index 96489321..4b58326e 100644
--- a/data/language-specs/c.lang
+++ b/data/language-specs/c.lang
@@ -244,6 +244,7 @@
       <keyword>void</keyword>
       <keyword>wchar_t</keyword>
       <keyword>wint_t</keyword>
+      <keyword>[a-z_][0-9a-z_]+(_t|_T)</keyword>
     </context>
 
     <context id="storage-class" style-ref="storage-class">